Mercury Emissions Control in Coal Combustion Systems Using Potassium Iodide: Bench-Scale and Pilot-Scale Studies
Mercury Emissions Control in Coal Combustion Systems Using Potassium Iodide: Bench-Scale and Pilot-Scale Studies
复制标题
DOI：
10.1021/ef800656v
复制
发表时间：
2009-01
期刊：
影响因子：
5.3
通讯作者：
Ying Li;Michael Daukoru;Achariya Suriyawong;P. Biswas
中科院分区：
文献类型：
--
作者：
Ying Li;Michael Daukoru;Achariya Suriyawong;P. Biswas
据报道，添加卤素或卤化物可促进燃煤发电厂的汞去除。在这项研究中，工作台和中试规模的实验进行了使用碘化钾（KI）捕获和去除空气和燃煤废气中的汞。使用了两个实验室规模的反应器系统：（1）填充有颗粒或粉末KI的填充床反应器（PBR）和（2）具有KI颗粒注入的气溶胶流动反应器（AFR）。结果发现，较高的温度，较高的KI浓度，和较长的气体停留时间导致在较高的汞去除效率。在高于300 °C的PBR中使用0.5g粉末KI和在高于500 °C的AFR中使用600的KI/Hg摩尔比在5.8s的停留时间下实现100%的Hg去除。KI相对于Hg的低注入比表明KI对于空气中的Hg去除是高度有效的。通过在高温下O2氧化KI形成I2蒸气，然后与Hg反应生成HgI 2，被确定为去除途径。在160 kW煤粉燃烧器上进行了中试试验。KI以两种方式引入：作为与煤混合的粉末和通过将KI溶液液滴喷射到烟气中。在这两种情况下，汞的去除效率随着KI的进料速率的增加而增加。发现将KI粉末与煤混合比将KI喷洒到烟道气中更有效，这很可能是由于较高的温度、KI的较长停留时间以及形成二次反应性吸附剂。在中试规模的试验中，KI对汞的去除效果不如在实验室规模的试验中，这可能是由于某些烟气成分与KI或I2发生反应。汞形态测量在两个实验室和中试规模的实验表明，没有氧化的汞在气相中引入KI后，这表明氧化产物碘化汞被捕获在颗粒相。这对配备静电除尘器的燃煤电厂非常有利，因为静电除尘器可以有效地去除颗粒中的汞。
Addition of halogens or halides has been reported to promote mercury removal in coal-fired power plants. In this study, bench- and pilot-scale experiments were conducted using potassium iodide (KI) for capture and removal of Hg in air and coal combustion exhaust. Two bench-scale reactor systems were used: (1) a packedbed reactor (PBR) packed with granular or powder KI and (2) an aerosol flow reactor (AFR) with injection of KI particles. It was found that a higher temperature, a higher concentration of KI, and a longer gas residence time resulted in a higher Hg removal efficiency. A 100% Hg removal was achieved in the PBR above 300 °C using 0.5 g of powder KI and in the AFR above 500 °C with a KI/Hg molar ratio of 600 at a 5.8 s residence time. The low KI injection ratio relative to Hg indicated that KI is highly effective for Hg removal in air. Formation of I2 vapor by the oxidation of KI by O2 at high temperatures, which then reacts with Hg to produce HgI2, was identified as the pathway for removal. The pilot-scale experiments were conducted in a 160 kW pulverized coal combustor. KI was introduced in two ways: as a powder mixed with coal and by spraying KI solution droplets into the flue gas. In both cases the Hg removal efficiency increased with an increase in the feed rate of KI. Mixing KI powder with coal was found to be more effective than spraying KI into the flue gas, very likely due to the higher temperature, longer residence time of KI, and the formation of a secondary reactive sorbent. The Hg removal by KI was less efficient in the pilot-scale tests than in the bench-scale tests probably due to certain flue gas components reacting with KI or I2. Hg speciation measurements in both benchand pilot-scale experiments indicated no oxidized mercury in the gas phase upon introduction of KI, indicating that the oxidation product HgI2 was captured in the particulate phase. This is very beneficial in coal-fired power plants equipped with electrostatic precipitators where particulate-bound Hg can be efficiently removed.